Model+ - Dynamic Trendlines

//version=5
indicator("Model+ - Dynamic Trendlines", overlay=true)

// === Helper: Detect Swing Highs and Lows ===
isSwingLow(idx) => low[idx] < low[idx - 1] and low[idx] < low[idx + 1]
isSwingHigh(idx) => high[idx] > high[idx - 1] and high[idx] > high[idx + 1]

// === Function to find trendlines ===
findTrendline(_isLow, length) =>
var float point1 = na
var float point2 = na
var int idx1 = na
var int idx2 = na
for i = length to 1 by -1
if _isLow ? isSwingLow(i) : isSwingHigh(i)
if na(point1)
point1 := _isLow ? low : high
idx1 := bar_index - i
else if na(point2)
point2 := _isLow ? low : high
idx2 := bar_index - i
break
slope = (point2 - point1) / (idx2 - idx1)
offset = bar_index - idx2
start = point2 + slope * (-offset)
end = point2 + slope * (1 - offset)
[start, end]

// === Dynamic detection per timeframe ===
timeframeName = timeframe.period
len = switch timeframeName
"D" => 50
"W" => 30
"M" => 20
=> 50

// === Detect trendlines ===
[startLow, endLow] = findTrendline(true, len)
[startHigh, endHigh] = findTrendline(false, len)

// === Draw lines ===
var line trendSupport = na
var line trendResistance = na

if not na(startLow) and not na(endLow)
line.delete(trendSupport)
trendSupport := line.new(x1=bar_index - 1, y1=startLow, x2=bar_index, y2=endLow, color=color.green, width=2, style=line.style_solid)

if not na(startHigh) and not na(endHigh)
line.delete(trendResistance)
trendResistance := line.new(x1=bar_index - 1, y1=startHigh, x2=bar_index, y2=endHigh, color=color.red, width=2, style=line.style_solid)

// === Support/Resistance Horizontal (based on swing points) ===
getHorizontalLevels(n) =>
var float support = na
var float resistance = na
for i = n to 1 by -1
if isSwingLow(i) and na(support)
support := low
if isSwingHigh(i) and na(resistance)
resistance := high
if not na(support) and not na(resistance)
break
[support, resistance]

[supportLine, resistanceLine] = getHorizontalLevels(len)

var line srSupportLine = na
var line srResistanceLine = na

if not na(supportLine)
line.delete(srSupportLine)
srSupportLine := line.new(x1=bar_index - len, y1=supportLine, x2=bar_index, y2=supportLine, color=color.green, style=line.style_dashed)

if not na(resistanceLine)
line.delete(srResistanceLine)
srResistanceLine := line.new(x1=bar_index - len, y1=resistanceLine, x2=bar_index, y2=resistanceLine, color=color.red, style=line.style_dashed)